Motor vehicle analyzers have been around in various forms for some time. The extensive incorporation of computer control, sensors and other electronic and electrical components into motor vehicles to control engines, transmissions, antilock brakes, and other vehicle operating systems has forever changed vehicle servicing. While analyzers used to be optional or convenient for motor vehicle servicing, they now are a virtual necessity for assisting a mechanic in analyzing vehicle operating problems.
The inability to perform comprehensive diagnostic testing of systems including such components in the field can result in great inefficiencies and expense. For example, it is often difficult to determine whether an operating problem resides in a vehicle's engine or transmission. As a result, a number of transmissions which are removed and returned to the factory for repair turn out to be fault free. In many of the remainder of the returned transmissions, the problem can be corrected by a minor adjustment at the factory which easily could have been made in the field had the proper diagnosis been made.
A complicating factor in diagnostic testing is the proliferation of many different computer and/or electronically controlled systems. Differences can be substantial for different makes of cars, for different models from the same manufacturer, and even the same model line from year-to-year. The different systems are generally accompanied by different interfaces and data formats that limit any particular testing unit to only a relatively small number of vehicles. Stocking a large number of different monitors to accommodate the various makes and models is expensive, inefficient and wasteful. However, it is oftentimes difficult if not impossible to perform adequate field service without the use of these analyzers as previously noted.
Another problem is the difficulty of simulating normal driving conditions within the confines of an automotive repair facility, while at the same time monitoring the various systems to determine the location and nature of any malfunctions. Also, many automotive problems are intermittent and do not show up in a single test run. Such intermittent problems require the monitoring of a vehicle's performance over a sufficient, possibly long, period of time and under particular conditions such that data representative of a failing or faulty component can be collected when an intermittent malfunction does occur to enable effective diagnostic analysis. Often an intermittent problem will require a large amount of time to diagnose. One problem with prior tests is that the tree structure of such testing requires a technician to follow several false leads to termination, wasting a lot of time and perhaps missing the cause of the problem if it does not occur when evaluating a particular branch of the structure.
Unfortunately, adding to all these problems is the fact that most tree structures leave the technician little discretion in the order of testing. This limitation may require the technician to make several tests which could easily be ruled out or given lower priority based on experience. Accordingly, appropriate data may not be collected for hard faults much less intermittent faults.
It is thus apparent that there is a continuing need for improved diagnostic methods and apparatuses which can be used to diagnose motor vehicle system problems. For simplicity sake, the diagnosis preferably would be based on vehicle operating or drive symptoms which can be readily identified by an operator of a motor vehicle or by service personnel.